Experiments are proposed to study the interaction between a heme Fe2 plus -NO and non-heme Fe2 plus -NO complex and cheemical carcinogenesis. Methods are proposed utilizing ESR-spin-labelling techniques that will allow the direct study of carcinogen binding to cellular component, i.e., membranes, nucleic acids and proteins. Studies are proposed which will involved a new technique for monitoring carcinogenic nitrosoamine production from nitrite ions and transport in vivo.